Data collection and analysis Data will be collected on the appropriate Case Report Form (CRF). In particular anamnestic information will be collected, data about surgery and post-operative clinical data, in particular respiratory parameters. Data will be analyzed with a professional statistical software. Dichotomous variables will be compared with the two-tailed Chi square test, using the Yates correction when appropriate. Continuous variables will be compared by analysis of variance or the non-parametric Kruskal-Wallis test, when appropriate.